"Telstar Electronics" wrote in message
...
Nonsense... please read the definition section at
http://minicircuits.com/pages/pdfs/doub9-2.pdf

You are grasping at straws trying to defend your beliefs. Their definition
only applies to their products. You should have read the entire article.
If you consider the single discontinuity of an ideal diode at the origin as
nonlinear, then you are correct. In practice, two Class AB or B
amplifiers, operated over their most linear region (each individually
producing harmonics and intermodulation over 40 dB down from the
fundamental), can be used in a push-push configuration to produce even
order harmonics. I believe "Stray Dog" and I both have shown that single
ended Class A amplifiers DO produce harmonics.

The Mini Circuits "doubler" is, I believe, essentially a full wave
rectifier using Schottky diodes. If the diodes were ideal, i.e. had no
highly non-linear region at low voltages, there would be no fundamental
output or odd order harmonics. From my earlier discussion of full wave
rectification, perfect diodes would produce the fourth harmonic 14 dB lower
than the second harmonic, and the sixth harmonic slightly over 7 dB down
from the fourth. The Minicircuits device produces at its output the
fundamental and odd order harmonics in addition to the desired even order
harmonics. It also requires a drive level of between 0 and 20 dBm. Too
low a drive and the doubling action disappears; too high a drive and the
amplitude of the higher harmonics increases (until the device burns out).

Some further research into the push-push doubler reveals that two sharp
cutoff pentodes would do a better job than triodes for this application.
Also junction field effect transistors follow square law characteristics
over a fairly wide range making them ideal in frequency doubler operation
too. It is also possible to nearly achieve ideal diode behavior with the
use of very high gain amplifiers with feedback through the diode. See the
following Intersil ap-note for details:
http://www.intersil.com/data/an/an1114.pdf.

My post of the graphs has not appeared on the "alt.binaries.ham-radio"
Usenet newsgroup, even on my nntp server which still insists that the
newsgroup exists. I'll try again using "alt.binaries.radio.misc" this
time. My thanks go to "Stray Dog" for his efforts in also experimenting
with a single ended 6C4 triode.

73, Dr. Barry L. Ornitz WA4VZQ